1. Field of the Invention
The exemplary embodiments disclosed herein are related to an apparatus and method for transporting and storing reduced-capacity substrate carriers for use within an IC fab.
2. Brief Description of Related Developments
There is a desire in the semiconductor industry to reduce wafer cycle time through the fab and reduce the amount of work in progress as well as to improve wafer safety. Studies have shown that by moving to a single wafer carrier, wafer cycle time and WIP (wafers in process) is significantly reduced. In addition for the next generation wafer size (450 mm) the ITRS roadmap calls for single substrate carriers. Benefits of using single wafer or reduced capacity carriers include WIP reduction, process changeover time reduction and product ramp time improvement. Problems arise where single substrate carriers are employed relative to the ability of both the process tool and material transport system to effectively maintain the higher pace of the factory due to the larger number of carrier transport moves as compared to 13 or 25 wafer carriers. One example of such a problem includes where there is only one slot. It is desired that the robot in the process tool have the capability to quickly swap (fast swap) the wafer in the carrier so the carrier may be able to be replaced with another carrier that has an unprocessed wafer to keep the tool busy. Many such tools do not have the ability to fast swap, as in the case of a conventional single blade three axis robot. Another example of such a problem includes where there is only one slot. It is desired that the material transport system transporting carrier to tools in the IC FAB have the capability to supply carriers, at a high rate and quickly swap the carriers at the process tools load port(s) so that one carrier at the tool may be able to be replaced with another carrier that has an unprocessed wafer to keep the tool busy. Many such material transport systems do not have the ability to supply carriers at a high rate or with the capability to fast swap, as in the case of a conventional (overhead transport) OHT based material transport systems as implemented in conventional 300 mm fabs.
Conversely conventional load ports, or carrier to tool interfaces, of conventional processing tools are not capable of handling (i.e. receiving, interfacing or reading for removal) a high rate supply of carriers desired when employing reduced capacity carriers in the FAB. One example of a conventional carrier to tool interface is disclosed in U.S. Patent Publication US 2003/0044261, published Mar. 6, 2003, wherein the semiconductor material handling system is an EFEM that may be mounted or integrated to the front end of a processing tool. The conventional EFEM disclosed has carrier (FOUP) I/O ports and pod advance plates corresponding to the I/O ports that register and shuttle pods for docking/undocking to the I/O ports. The above noted example is representative of conventional carrier-tool interfaces of conventional processing tools. The I/O ports to which the pods are mated (for loading/unloading substrates or wafers to the tool) are linearly or axially distributed. By way of example, for each unit width (corresponding to the carrier width) along the carrier-tool interface frontage there is but one I/O port. Hence, in conventional tools but a single carrier is interfaced per unit width of the tool front. This linear interface geometry is very limiting to tool load unload when the carriers being used are of reduced capacity. Further, the employment of pod advance plates for pod docking to I/O ports, in the conventional interfaces, typically involves pod registry along two planes (i.e. seating interface between pod and advance plate and port interface between pod and port), a condition which is overconstrained by its very nature with a corresponding deleterious affect on the rate of carrier supply to the tool. Also, the time involved in first registering a pod to the pod advance plate, and then having the pod advance plate bring the pod into contact/registry with the I/O port again impacts on the achievable rate of carrier supply. These are but some of the problems of conventional carrier-tool interfaces overcome by the exemplary embodiments as will be described in greater detail below.
Other examples of transport systems, carriers and openers may be found in U.S. Pat. No. 6,047,812; RE38,221 E; U.S. Pat. Nos. 6,461,094; 6,520,338; 6,726,429; 5,980,183; United States Patent Publications 2004/0062633, 2004/0081546, 2004/0081545; 2004/0076496 and pending Brooks Automation application Ser. Nos. 10/682,808 all of which are incorporated by reference herein in their entirety.